NativeAOT TODO list

[jonathanpeppers]

What do we need to do for NativeAOT?

• dotnet new android && dotnet publish -p:PublishAot=true
• dotnet new maui runs: [WIP] turn NativeAOT sample into a .NET MAUI app #9747
• Parse Android system properties like debug.mono.log, to disable lref/gref logging
• MSBuild warning for non-Mono runtimes, that says "experimental"
• Default $(PublishAotUsingRuntimePack)=true, and see what xamarin/xamarin-macios does
• Get Mono.Android-Tests running on NativeAOT
• Mono-specific startup settings like Timezone notifications, unhandled exceptions, System.Threading.Tasks SyncContext.
• Solve all NativeAOT trimmer warnings

[jonpryor]

Alternate "MVP 1.1" typemap idea, for posterity: instead of a Dictionary<string, Type>, have two fields:

1. Dictionary<string, RuntimeTypeHandle> or string[]+RuntimeTypeHandle[] pair, plus
2. Dictionary<string, Type>

The linker step would populate (1), which might be faster because RuntimeTypeHandle is a stuct.

At runtime, consult (2) first, and if a type mapping doesn't exist, use (1) to lookup the RuntimeTypeHandle + Type.GetTypeFromHandle(RuntimeTypeHandle), caching the result in (2).

Questions:

• Can we lookup the RuntimeTypeHandle value from Cecil?
• The caching will require locking. What kind of overhead will this imply?

[jonathanpeppers]

There must be a way to use a TypeHandle with Mono.Cecil, as the IL "typemap MVP 1.0" is writing is doing this:

android/src/Microsoft.Android.Sdk.ILLink/TypeMappingStep.cs

Lines 70 to 83 in 70bd636

	/*
	* IL_0000: ldarg.0
	* IL_0001: ldfld class [System.Runtime]System.Collections.Generic.IDictionary`2<string, class [System.Runtime]System.Type> Microsoft.Android.Runtime.NativeAotTypeManager::TypeMappings
	* IL_0006: ldstr "java/lang/Object"
	* IL_000b: ldtoken [Mono.Android]Java.Lang.Object
	* IL_0010: call class [System.Runtime]System.Type [System.Runtime]System.Type::GetTypeFromHandle(valuetype [System.Runtime]System.RuntimeTypeHandle)
	* IL_0015: callvirt instance void class [System.Runtime]System.Collections.Generic.IDictionary`2<string, class [System.Runtime]System.Type>::Add(!0, !1)
	*/
	il.Emit (Mono.Cecil.Cil.OpCodes.Ldarg_0);
	il.Emit (Mono.Cecil.Cil.OpCodes.Ldfld, field);
	il.Emit (Mono.Cecil.Cil.OpCodes.Ldstr, javaKey);
	il.Emit (Mono.Cecil.Cil.OpCodes.Ldtoken, module.ImportReference (typeDefinition));
	il.Emit (Mono.Cecil.Cil.OpCodes.Call, getTypeFromHandle);
	il.Emit (Mono.Cecil.Cil.OpCodes.Callvirt, addMethod);

[filipnavara]

Ldtoken returns RuntimeTypeHandle so you can use that in the dictionary. It's, however, not a pattern that can be represented in C# and ILSpy will not decode it correctly.